Drainage system and apparatus for treating runoff

Abstract

A drainage system, comprising a collector which is arranged to collect liquid and a drainage pipe having a pipe inlet that opens into the collector such that liquid collected by the collector drains through the pipe inlet. The drainage pipe is provided with a vent spaced away from the pipe inlet. The vent is arranged such that, when liquid collected by the collector occludes the pipe inlet, liquid flowing through the drainage pipe draws air into the drainage pipe through the vent.

The invention claimed is: 
     
       1. An apparatus for treating runoff, comprising:
 a downpipe having a downpipe inlet and a downpipe outlet; 
 a treatment vessel; and 
 an energy dissipater disposed within the treatment vessel such that, in normal use, the energy dissipater is submerged by liquid which accumulates within the treatment vessel, the energy dissipater comprising a substantially cylindrical dissipation chamber having a dissipater inlet provided in fluid communication with the downpipe outlet, and a dissipater outlet arranged to discharge fluid into the treatment vessel, wherein the dissipation chamber comprises a tube having at least one open end of which provides the dissipater outlet, wherein the dissipater inlet of the energy dissipater is arranged to discharge fluid into the tube of the dissipation chamber in a tangential direction with respect to the longitudinal axis of the tube so as to promote rotational flow of liquid entering the tube of the dissipation chamber through the dissipater inlet. 
 
     
     
       2. An apparatus as claimed in  claim 1 , wherein the dissipater inlet is arranged to promote rotational flow of liquid entering the dissipation chamber. 
     
     
       3. An apparatus as claimed in  claim 1 , wherein the tube includes at least two open ends, wherein each end of said at least two open ends provides a dissipater outlet. 
     
     
       4. An apparatus as claimed in  claim 1 , wherein the energy dissipater is suspended within the treatment vessel by the downpipe. 
     
     
       5. An apparatus as claimed in  claim 1 , wherein the treatment vessel comprises a collection chamber and a drainage chamber which has a drain outlet, wherein the collection chamber and the separation chamber are separated by a baffle which defines a weir such that liquid which collects in the collection chamber above the level of the weir flows over the weir and is discharged from the treatment vessel through the drain outlet. 
     
     
       6. An apparatus as claimed in  claim 5 , wherein a vortex valve is disposed at the drain outlet to control flow through the drain outlet. 
     
     
       7. An apparatus as claimed in  claim 5 , wherein the apparatus comprises an overflow disposed within the collection chamber. 
     
     
       8. An apparatus as claimed in  claim 5 , further comprising a drainage valve provided at a lower region of the collection chamber which can be opened to drain liquid collected by the collection chamber. 
     
     
       9. An apparatus as claimed in  claim 1 , wherein the treatment vessel includes an upper portion that includes a receptacle for receiving a growing medium. 
     
     
       10. An apparatus as claimed in  claim 9 , wherein the receptacle includes a planting tray.